1. Field of the Invention
The present invention relates to an improved solar thermal collector which allows the use of plastics and rubber materials that need to be kept at safe temperatures to allow for a long life.
2. Description of the Prior Art
The tremendous increase in concern for our environment and the resultant pressure on utilities to reduce pollution and even to close nuclear plants is opening a large market for renewable energy products that are cost effective. Previous solar thermal collectors used heavy glass and aluminum extrusions as well as expensive copper as their primary components. These components not only made the collectors heavy and expensive but also difficult to install. It is necessary to make available collectors using less expensive plastic and rubber materials to truly open up a large solar market.
A previous invention by Albert C. Rich, "Solar Water Heating System" U.S. Pat. No. 4,930,492 allowed for the satisfactory use of a rubber absorber plate by the use of a special floating valve. The system worked well but it became apparent that high stagnation temperatures over 250 degrees could result in the reduced life expectancy of the rubber collector absorber and plastic glazing materials. To protect against this situation the inventor devised a simple passive venting system that takes advantage of the natural tendency of the two walled ("Twinwall") transparent plastic glazing to bow. This never before devised venting system effectively solves the last barrier to the use of plastic and rubber materials in solar thermal collectors. One of the reasons it was never devised before is similar to the reason the inventors floating valve had never been devised before, that is because the need for the item had never been recognized in a solar application.